MIPS: Move 'gic_frequency' to common location.

Move the global variable 'gic_frequency' to be defined in the file
'arch/mips/kernel/irq-gic.c' instead of defining it individually
for each platform making use of the GIC. Also change the type to
be an unsigned integer instead of signed.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
diff --git a/arch/mips/include/asm/gic.h b/arch/mips/include/asm/gic.h
index a05f97d..f1a1e98 100644
--- a/arch/mips/include/asm/gic.h
+++ b/arch/mips/include/asm/gic.h
@@ -360,6 +360,7 @@
 #define GIC_PIN_TO_VEC_OFFSET	(1)
 
 extern unsigned int gic_present;
+extern unsigned int gic_frequency;
 extern unsigned long _gic_base;
 extern unsigned int gic_irq_base;
 extern unsigned int gic_irq_flags[];